DESCRIPTION (Applicant's Abstract): Policy makers, program managers, community planning group members and other key decision makers need to balance the cost and effectiveness of various interventions when planning and evaluating HIV prevention programs. Resources to fund HIV prevention programs are limited and must be used judiciously in order to maximize the number of HIV infections averted. Economic evaluation studies of HIV prevention interventions can provide some of the information needed by key decision makers. Unfortunately, little such information is currently available, and few ongoing behavioral studies have an economic evaluation component. NIMH has funded a major, multi-site, randomized controlled trial to compare a seven-session, cognitive-behavioral, HIV prevention intervention to a one-session, educational, HIV prevention intervention. Within each of the seven study sites, three populations are served and enrolled in the trial: women attending primary health care facilities; women attending STD clinics; and men attending STD clinics. No study participant is less than eighteen years of age. The 12 month follow-up period for the trial will soon be ending. Major outcomes measures include: numbers of sex partners in the past 90 days, number of acts of vaginal and anal intercourse with each partner; and proportion of acts during which condoms were used. Self-report of injection drug use were also collected. Some information about non-HIV STDs was also collected via chart review and urinalysis (for some populations at certain time periods.) The investigators propose to augment this trail with a retrospective cost-effectiveness analysis. The cost of the treatment and control interventions will be estimated retrospectively using published and unpublished documentation about intervention delivery. The behavioral outcome data will be mapped into health outcomes (e.g., estimated number of HIV infections averted) using mathematical modeling techniques. The estimated cost and health outcomes for each intervention, for each specific population, will be combined using standard methods of cost-utility analysis (CUA). CUAs contain estimates of how much the intervention cost for each quality adjusted life year (QALY) saved. In this case the CUA will be incremental. That is, it will compare the additional cost of the treatment intervention (relative to the control intervention) to the additional QALYs saved by the treatment intervention (relative to the control intervention). The proposed research program will include publication of the cost-utility analysis results in scientific journals, and will include a special dissemination plan for results.